Contact assembly with grounding conductor support

ABSTRACT

A contact assembly with at least one signal contact and at least one ground contact, in particular for use in a connector or the like, comprises a support of resilient conductive material, an insulating intermediate layer provided on the support and at least one signal conductor supported on the insulating intermediate layer. The support is used as ground conductor and two or more adjacent contacts pads are provided for each signal conductor or each group of signals conductors adjacent a first edge of the support. One contact pad is connected with the support and the other contact pad(s) is (are) connected to the respective signal conductors.

The invention relates to a contact assembly, in particular for use in aconnector or the like, comprising at least one signal contact and atleast one ground contact.

Such contact assemblies are generally mounted in the housing of aconnector element, wherein the contacts are made as a male or a femalecontact. In the design of the known contacts attention has mainly beenpaid to the mechanical aspects of the connector assembly equiped withsaid contacts, in particular with respect to the forces required forcoupling and decoupling the connector elements. Attention was only paidto the electrical aspects in that one aimed at realizing good reliableconnections between the contacts of both connector elements. Withincreasing speeds of the digital signals to be transferred, i.e.decreasing rise times, the electrical performance of the contacts as acircuit element becomes important. In the known connector assembliesproblems occur with higher signal speeds with respect to cross-overbetween signal contacts, transmission losses, reflections and groundbounce or switching noise. Up to the present it is attempted to obviatethese problems by mounting the signal and ground contacts in a suitabledistribution in the connector elements, wherein however these problemscannot be eliminated below rise times of 0.6 ns.

European patent application 91200396 of the same applicant discloses aconnector assembly, wherein these problems are obviated in that outersignal conductors connected to ground are provided, each of said outersignal conductors enclosing one or more signal contacts. Although saidproblems are eliminated in an effective manner by this connectorassembly, the number of signal connections per unit surface in thisconnector assembly is restricted.

The invention aims to provide a contact assembly of the above-mentionedtype, wherein said problems which may occur at high speeds when used ina connector, can be eliminated by such a construction of the contactassembly itself that the performance of each signal contact as a circuitelement can be predetermined and said signal distortions can beminimized, whereas moreover the number of signal connections per unitsurface can be significantly increased.

To this end, the invention provides a contact assembly with at least onesignal contact and at least one ground contact, in particular for use ina connector or the like, comprising a support of resilient conductivematerial, an insulating intermediate layer provided on the support andat least one signal conductor supported on the insulating intermediatelayer, wherein the support is used as ground conductor characterized inthat two or more adjacent contact pads are provided for each signalconductor or each group of signal conductors adjacent a first edge ofthe support, wherein one contact pad is connected with the support andthe other contact pad(s) is (are) connected to the respective signalconductors.

In this manner a contact assembly is obtained, wherein a signalconductor with the opposite support part separated from said signalconductor by the intermediate layer, forms a transmission line, whereina desired impedance of 50 or 75 ohm, for example, can be obtained by asuitable choise of the thickness of the insulating intermediate layerand the width of the signal conductor. Thereby, the electricalperformance of the contacts can be taken into account in designing theoverall system from the beginning. The above-mentioned signaldistortions will not occur at the contacts according to the invention.

Actually, the mechanical and electrical functions of the signal contactsare separated in the contact assembly according to the invention,wherein the support performs the mechanical functions for the signalcontacts and operates further as ground contact. The signal conductorsoperating as signal contacts can be designed for optimal signaltransmission properties, wherein it is not necessary to take themechanical properties into account. Thereby an excellent signalintegrity can be guaranteed, because the signal contacts have acontrolled impedance and moreover a low capacity and low inductance.Further the contact assembly according to the invention has theimportant advantage that a connector with a high density of signalcontacts can be manufactured, because actually all contacts are signalcontacts and no space is occupied by separate ground contacts. Themanufacturing costs of the contact assembly according to the inventionare relatively low, because a tooling change is not required to obtaincontacts with different electrical properties or a different pattern ofground and signal connections.

The invention will be further explained by reference to the drawings inwhich some embodiments of a contact assembly according to the inventionare schematically shown.

FIG. 1 is a perspective view of an embodiment of the contact assemblyaccording to the invention in a flat position, wherein the pattern ofsignal conductors and contact pads can be seen.

FIG. 2 schematically shows the use of the contact assembly of FIG. 1 ina connector element.

FIG. 3 is a top view of an alternative embodiment of the contactassembly according to the invention.

FIG. 4 is a perspective view on a larger scale of one longitudinal edgeof the contact assembly of FIG. 3.

FIG. 5 schematically shows the use of two contact assemblies of FIG. 3in a connector element.

FIG. 6 is a perspective view of a third embodiment of the contactassembly according to the invention.

FIG. 7 schematically shows the use of the contact assembly of FIG. 6 ina connector element.

FIGS. 8 and 9 schematically show a perspective view and a side view,respectively, of two different embodiments of the contact assemblyaccording to the invention.

FIG. 10 schematically shows the use of a variant of the contact assemblyof FIG. 9 in a connector element.

FIG. 11 perspectively shows a further embodiment of the contact assemblyaccording to the invention.

FIG. 1 shows a first embodiment of the contact assembly 1 comprising astrip-like support 2 and an insulating intermediate layer 3, upon whichsignal conductors 4 and contact pads 5 and 6 are provided. FIG. 1 showsthe support 2 in perspective in a flat position, whereas FIG. 2 showsthe contact assembly 1 as applied in a connector element 7 of theso-called direct edge type, wherein the support 2 has been given adesired shape for contacting an edge of a printed circuit board.

Slits 8 are provided at the opposite longitudinal edges of thestrip-like support 2, whereby fingers 9 are obtained each carrying acontact pad 5 and a contact pad 6. As appears from FIGS. 1 and 2 eachcontact pad is provided with a contact button 10, wherein the strip-likesupport 2 is shaped in such a manner that the contact pads 5, 6 with thecontact buttons 10 protrude so that as used in the connector element 7the contact buttons 10 can contact corresponding contact pads of aprinted circuit board 11 inserted into the connector element 7.

From FIG. 1 it appears that the contact pads 5 are connected with thesignal conductors 4. In the embodiment shown the contact pads 6 areconnected with the support 2 through a conductive plating of a holeindicated by a circle.

The contact pads 5 form signal contact pads, while the contact pads 6form ground contact pads. The signal conductors 4 are connected withcontact pins 12 substantially in the centre part of the support 2, whichcontact pins 12 project through openings 13 formed in the support 2without contacting the material of the support 2. Ground contact pins 14connected with the support 2 are provided between signal contact pins 12of the signal conductors 4 successive in the longitudinal direction ofthe support 2.

The contact pins 12, 14 are inserted in plated through holes of aprinted circuit board 15 and are connected with the circuit paths ofthis printed circuit board 15 in this manner.

The support 2 consists of a resilient conductive material, for exampleberyllium-copper which provides the mechanical strength and resiliencefor the signal conductors 4. The signal conductors 4 and the contactpads 5, 6 are made from a conductive layer, for example copper, which isprovided on the insulating intermediate layer 3.

FIG. 3 shows a top view of a contact assembly 16 which in the samemanner as contact assembly 1 comprises a strip-like support 2 with aninsulating intermediate layer 3 upon which signal conductors 4 areprovided. At one longitudinal edge contact pads 5 and 6 are alsoprovided, wherein the contact pads 5 are connected with the signalconductors 4 and the contact pads 6 are connected through a shortconductor 17 with the longitudinal edge 18 of the support 2 projectingbeyond the insulating layer 3. At the opposite longitudinal edge of thesupport 2 contact pads 19 and 20 made as projecting contact tongues areprovided, wherein the contact pads 19 are connected with the signalconductors 4 and the contact pads 20 are connected with the support 2.The longitudinal edge with the contact pads 19, 20 is shown at a largerscale in FIG. 4 showing that the contact pads 19, 20 consisting ofconductive material are attached to the insulating intermediate layer 3,for example by bonding. In this case the insulating intermediate layer 3will preferably consist of a layer coated with conductive material onboth sides, wherein the support 2 is attached on one side by means of aconductive adhesive 21.

It will be understood that the proportions of the different layers inFIG. 4 are not shown to scale.

It is further noted that the contact pads 20 can be made out of thesupport 2 as an alternative. In this case, it is further possible toform supports for the contact pads 19 out of the support 2, so that thecontact pads 19, 20 can operate as contact springs.

FIG. 5 shows an application of the contact assembly 16 showing that thesupport 2 just as in the contact assembly 1, is shaped at the locationof the contact pads 5, 6 in such a manner that these contact padsproject, so that they can contact corresponding contact pads of aprinted circuit board 23 inserted into a connector 22. The contact pads19, 20 are connected with contact pads of a printed circuit 24 in amanner not further shown.

The connector shown in FIG. 5 is a so-called zero insertion force typeconnector, wherein a moveable element 25 is provided, which is in ahigher position when the printed circuit board 23 is not inserted sothat the legs 26 press the contact assemblies 16 away.

Slits 27 are provided on both longitudinal edges of the support 2 sothat fingers 28 are obtained each carrying a contact pad 5 and a contactpad 6 or a contact pad 19 and a contact pad 20, respectively.

FIG. 6 shows a contact assembly 29 to be used in a so-called indirectconnector 30 as shown in FIG. 7. In this case the contact assembly 29comprises a support 2 with an insulating intermediate layer 3 havingcontact pads 19, 20 on one longitudinal edge provided in the manner asshown in FIG. 4. These contact pads 19, 20 are connected withcorresponding contact pads of a printed circuit board 31 by soldering.The contact pads 19 and/or 20 can be made as contact springs in the samemanner as described with respect to FIG. 4 for connection to the contactpads of the printed circuit board 31. At the opposite side male contacts32 are made out of the support 2, wherein the signal conductors 4 extendfrom the contact pads 19 upto adjacent the end of the contact pins 32.

FIG. 8 shows in perspective a contact assembly 33 according to theinvention which is provided with a female contact element 34 adapted tocooperate with a contact pin 32 of the contact assembly 29. Each contactassembly 33 comprises a support 2 partially coated with an insulatingintermediate layer 3, on which a signal conductor 4 is formed. A contactpin 35, for connection to a printed circuit board not shown is formedout of the support 2 at one longitudinal edge. At the same side of thesupport 2 a contact pin 36 is provided which is connected with thesignal conductor 4 by welding or the like and which extends through anopening formed in the support 2 without contacting the support 2. At theother side of the support a contact pad 5 is provided on theintermediate layer 3. In the embodiment shown, the edge of the support 2without the intermediate layer 3 is bent along 180° back towards theinsulating intermediate layer 3 in such a manner that a mainly u-shapededge 34 is obtained. At the location of the contact pad 5 the web 37 ofthe u-shaped edge 32 is provided with an opening for the passage of acontact pin 32, wherein the signal conductor 4 of the contact pin 32will contact the contact pad 5 and the material of the support 2 willcontact the free leg 38 of the u-shaped edge 34.

It will be clear that a number of contact assemblies 33 can beaccommodated in a connector in a usual manner.

FIG. 9 shows an alternative contact assembly 39 to be used incombination with the contact assembly 29. The contact assembly 39 isprovided with a u-shaped edge 34 in the same manner as the contactassembly 33. At the other longitudinal edge of the support 2 there arehowever provided contact pads 5, 6 on the insulating intermediate layer3 in the same manner as in the contact assembly according to FIGS. 1 and2 instead of contact pins, which contact pads 5, 6 are not visible inFIG. 9 and which are connected with the signal conductors 4 and thesupport 2, respectively.

FIG. 10 shows a contact assembly 40 corresponding with the same of FIG.9, wherein in this case contact pins 41 for connection to a printedcircuit board are formed out of the edge opposite of the u-shaped edge34. The insulating layer 3 only has signal contact pads 5 in this case,which contact pads 5 are connected with the signal conductors 4. FIG. 10further shows a suitable housing 42 for the contact assembly 40. Whenthe contact pins 41 are provided with a press-fit portion known per se,this embodiment has the advantage that the contact pins 41 also providethe required contact pressure for the contact pads 5.

Finally FIG. 11 shows in perspective a contact assembly 43, the support2 of which is provided at one longitudinal edge with contact pins 44 forconnection to a printed circuit board in the same manner as the contactassembly 40. At the other longitudinal edge male contact pins 32 areformed out of the support in the same manner as in the contact assembly29 of FIG. 6. The signal conductors 4 extend along these contact pins 32and end at a bent part 45 in contact pads 5 in the same manner as in thecontact assemblies 39 and 40.

It is noted that the contact assemblies 33, 39 shown in FIGS. 8 and 9can be made as a strip of contact assemblies in the same manner as withthe contact assembly 43.

From the foregoing it will be clear that the invention provides acontact assembly wherein each signal conductor 4 with the opposite partof the support 2 separated from the same by the intermediate layer 3forms a transmission line, wherein a desired impedance can be obtainedby a suitable choice of the thickness of the insulating layer 3 and thewidth of the signal conductor 4. If polyimide is used as material forthe intermediate layer 3 a thickness including any adhesive of 50 micronand a width of the signal conductor 4 of 200 micron results in animpedance of approximately 50 ohm. Thereby the electrical performance ofthe contacts can be taken into account from the beginning in designingthe overall system from which the contact assembly forms a part. Signaldistortions due to cross-over, transmission losses, reflections andground bounce or switching noise will hardly occur.

The support 2 consisting of a resilient conductive material can bedesigned for optimum mechanical characteristics and the signalconductors 4 can be designed for optimum characteristics for signaltransmission. An excellent signal integrity for the contacts of thecontact assembly according to the invention is guaranteed because thecontacts besides a controlled impedance further have a low capacity andlow inductance. A connector equipped with the contact assembly accordingto the invention can have a high density of signal contacts becauseactually all contacts are signal contacts. The manufacturing costs ofthe contact assembly according to the invention are relatively lowbecause a tooling change is not required to obtain contacts withdifferent electrical properties. The signal conductors and contact padscan be formed in any desired pattern of the support 2.

It is noted that the several above-mentioned contact pins for connectionto a printed circuit board can be provided with a press-fit portion in ausual manner.

Although in the above-described embodiments all signal conductors 4operate as signal conductors, it is also possible to provide betweeneach two adjacent signal conductors a signal conductor connected toground in order to obviate any possible cross-over between signalconductors.

The invention is not restricted to the above-described embodiments whichcan be varied in a number of ways within the scope of the followingclaims.

We claim:
 1. Contact assembly for use in a connector, the assemblycomprising a support of resilient conductive material, an insulatingintermediate layer provided on the support and at least one signalconductor supported on the insulating intermediate layer, wherein thesupport is used as a ground conductor characterized in that the supporthas a first edge provided as a plurality of parallel fingers, eachfinger having at least a portion of a signal conductor thereon and atleast two adjacent contact pads for each signal conductor, the pads oneach finger being adjacent the first edge of the support, wherein onecontact pad of each of the adjacent pads is connected with the supportand the other contact pad is connected to the respective signalconductor.
 2. Contact assembly according to claim 1, wherein, at asecond edge of the support for at least one of each signal conductor,contact pads for the support and the corresponding signal conductor(s),respectively, are provided for connection to corresponding contact padsof a printed circuit board.
 3. Contact assembly according to claim 1wherein the support is bent in such a shape at the location of thecontact pads that said contact pads protrude for contactingcorresponding contact pads of a complementary contact area.
 4. Contactassembly according to claim 1 wherein the support is made as a strip,and wherein said fingers are separated from each other by slits. 5.Contact assembly according to claim 4 wherein a second set of fingersare formed at a second edge of the strip-like support, and wherein saidsecond set of fingers are separated from each other by slits and eachfinger of said second set carries at least one of said contact pads. 6.Contact assembly according to claim 4, wherein contact pads (19, 20) areprovided on both sides of the strip-like support at the first edge,wherein said signal conductors (4) extend from the corresponding contactpads (19) to an opposite edge (18) of the support (2).
 7. Contactassembly according to claim 6 wherein said contact pads connected withthe support are formed out of the support.
 8. Contact assembly accordingto claim 6 wherein the contact pads located at the first edge of thesupport are contact tongues (19, 20).